The task of the military historian is beginning to look a trifle odd because the world is moving out from under him. Statesmen who have at their disposal intercontinental missiles with atomic warheads are not apt to find much nourishment in studies of conventional strategy. The lessons of even the most recent war—painstakingly studied and evaluated with profound thought—seem as out of date as an instruction in the tactical necessities of the Carthaginian war galleys. Only an optimist can believe that men will never again make war, but the one certainty seems to be that they will not again make war as they made it in the past. What is there, outside of the field of purely antiquarian interest, for the military historian to say?

Quite a lot, actually; for the ends which are sought by international violence are just about what they always were, and if the means by which these ends are to be gained have changed beyond recognition, the method of applying them still has to follow certain basic principles. Also, it is still necessary for a nation that wins a victory to do a little thinking about the uses to which the victory will finally be put.

In any case, the military historians continue to write, and they bring out books that deserve attention. In Key to Victory , Lieutenant Commander P. K. Kemp examines the ways in which Britain (with, it must be said, a little help from outside sources) exerted control of the sea lanes during World War II and the results that flowed from that control, and he writes in terms that are eminently meaningful today.

Commander Kemp is no old sea dog talking in terms of battleships and the Nelson touch. When he speaks of sea power, he means the manner in which a nation or an alliance denies to its enemy the use of the sea as a means of transport while retaining it for its own use. This remains “sea power” even though the airplane, the island base, intricate shore-mounted installations, and sundry other modern devices may be just as important as the water-borne fighting ship; and Commander Kemp quite rightly sees it as the great essential to victory in the war against the Axis powers. In the end, he argues, Hitler was defeated just as Napoleon was; he was not free to use the sea lanes and his opponents were, so that his conquests on dry land eventually became meaningless and the war was brought home to him with a force he could not match.

Key to Victory: The Triumph of British Sea Power in World War II , by Lieutenant Commander P. K. Kemp. Little, Brown and Co. 383 pp. $6.00.

Specifically, says this writer: back in 1940, when only England stood between Germany and final triumph, Hitler could not quite starve the British Isles into submission or mount the invasion which would have mashed the last center of resistance. He came fearfully close to it, but he never quite made it, and England’s situation even in her darkest hour reminds Commander Kemp of the remark made 150 years earlier by the Earl of St. Vincent, who was First Lord of the Admiralty when Napoleon was meditating a cross-Channel thrust. Being asked about the possibility of an invasion, St. Vincent drily said that invasion was a military question on which he was not competent to express an opinion; all he knew was that an invasion could not come by sea.

So in North Africa, where Rommel would have gone on to finish his conquest if the Axis had had real control of the supply lines across the Mediterranean; so also with Russia, to whom the flow of essential supplies was maintained in spite of appalling obstacles; and so finally with the great tide of soldiers and munitions that came from America, from Canada, and from Australia to tip the balance against the man who appeared to have conquered Europe. The story would have been very different if the seas had been a barrier for the Allied powers and not a highway.

That there were serious gaps in this highway from time to time is of course obvious. The straits to which the British were driven in the Mediterranean did at times look like the beginning of the end; the fearful losses in the North Atlantic sea lanes brought even Churchill himself to the verge of despair; and the story of the convoys to Russia contains chapters that still put a shiver down one’s back, even at this distance in time. But the gaps were always bridged, somehow, and the endurance and heroism that bridged them compel one’s dazzled admiration.

That Hitler was never able to exploit these gaps adequately was at least partly due, Commander Kemp believes, to the fact that Hitler had no real notion of what sea power meant. The one German in high command who might conceivably have won the war for him was, says Commander Kemp, Grand Admiral Raeder, commander in chief of the German Navy in the early years of the war and a man who understood clearly how a genuinely balanced navy—submarines, surface ships, and airplanes, working to a coherent plan based on genuine sea strategy—could have turned the tables. Hitler never comprehended what Raeder was talking about, displaced him finally with Doenitz, and in effect reduced the Navy to a submarine service. The German submarines did great things, but unsupported they were never quite enough.

For Britain’s failure to maintain her armed forces in the decades preceding the outbreak of World War II, this writer has strong condemnation. The explanation of the shabby deal at Munich, he insists, is to be found in the report Britain’s chiefs of staff gave Prime Minister Chamberlain when Germany was preparing to swallow Czechoslovakia. Without qualification, these men said that England was not ready for war and that any involvement in war with Germany at that time would probably lead to defeat. In effect, Chamberlain was told that he had to avoid war at all costs. He did it, to the total destruction of his own reputation; and Commander Kemp feels that he could not possibly have done anything else.

Naturally enough, this book concentrates on the British side of the story. As a picture of the war as a whole it is of course inadequate; what the armies did, in Russia or in France or elsewhere, is merely sketched in, and the manner in which control of the seas was finally won is described largely—though by no means entirely—in terms of what the British Navy did. But that, after all, is the story Commander Kemp selected, and he has told it very well. He is insistent in pointing out that sea power is not just a matter of navies. “In modern war,” he says, “the true exercise of maritime power depends nearly as much upon the exertions of land and air forces as it does upon naval.” But it is still sea power.